Machine for abrading photoengraving cylinders



May 13 1941- F. E. YETTER 2,241,568

MACHINE FOR ABRADING PHOTOENGRAVING CYLINDERS FiledOct. 2l, 1937 4 Sheets-Sheet 1 /INVEA/ro'e: Fen/wf E. YfrrE-e,

,4r ro @van May 13, 1941. F. E. YETTER 2,241,568

MACHINE FOR ABRADING PHOTOENGRAVING CYLINDERS Filed Oct. 2l, 1937 4 Sheets-Sheet 2 TTORNE K May 13, 1941. F. E. YETTER 2,241,563

MACHINE FOR ARADING PHOTOENGRAVING CYLINDERS Filed Oct. 21, 1957 4 Sheets-SheetI 3 l F. E. YETTE R May 13, 194i.

4 Sheets-Sheet 4 Filed Oct. 21. 1937 MACHINE FOR BRADING PHOTOENGRAVING CYLINDERS Patented May 13, 1941 UNITED STAT QFFICE MACHINE FOR ABRADING PHOTOENGRAV- ING CYLINDERS Frank E. Yetter, St. Louis, Mo., assignor to The Pulitzer Publishing Company, St. Louis, Mo., a corporation of Missouri The present invention relates to a novel method and means of obtaining a desired finish on photoengraving cylinders, and the like.

It is Well recognized that to obtain a desirable reproduction by photoengraving cylinders, it is Y.

necessary that the outer coating or surface be microscopically smooth. Otherwise, blemishes in such surface will produce faults in the pictures obtained from the cylinder. Heretofore the practice in putting the final polish on the cylinders has involved the use of a rotating disc of an abrasive material carried over the cylinder by a moving head, While the cylinder rotates. Inevitably, such a rotating head produces intersecting abrasive lines on the surface. tersections entrap ink when the cylinder is later used, which ink prints out in the final picture to pro-duce a naw therein.

The present method comprehends abrading the cylinder in such wise as to void such intersecting abrasive grooves. More particularly, it produces grooves, if any, that are unidirectional and so related to the surface of the cylinder as not to entrap any ink when the cylinder, after engraving, is rotated against the cleaning knife.V

This method is effected by means of an endless belt abrasive that is caused to pass across the surface of the cylinder and simultaneously to be carried axially thereof. 'I'he result is that any abrasive lines that appear in the surface all vide Va method of polishing photoengraving cylinders in such Wise as to minimize the production of abrasive scoring, and to avoid the presence of any intersecting abrasive lines. More specifically, it is an object to provide a method wherein any abrasive lines will be unidirectional and transverse to a generatriX of the cylinder.

A further object is to provide a method of the kind described, including a buiiing operation wherein any abrasive lines are automatically filled in by the material on the surface of the cylinder.

A further object of the invention is to provide a mechanism for producing the above method in a most advantageous form, which mechanism includes an endless belt abrasive with means to move the same substantially transversely to a generatrix of the cylinder. It is further an object to produce relative movement between the moving belt and the cylinder axially of the cylinder.

These in- It is a further object of the invention to provide means to adjust the tension of the belt and also to provide means to adjust the degree of Contact between the belt and the cylinder surface.

It is a further object of the invention to provide a belt that will at least substantially eliminate any edge produced abrasive lines and a further object is to provide buing belts of unique characteristics for use in producing an absolutely smooth surface.

Other objects will appear from the drawings and description to follow.

In the drawings:

Fig. 1 is a plan view of the mechanism;

Fig. 2 is an end view taken from the right of Fig. 1;

Fig. 3 is an end View taken from the left of Fig. l and showing the device partly in section;

Fig. 4 is a section on one of the abrasive hea-d rollers taken on the line 4 4 of Figs. 2 and 3;

Fig. 5 is a broken section through the abrasive head taken on the line 5 5 of Fig, 1;

Fig. 6 is an enlarged view of a contact adjusting mechanism partly in section;

Fig. 7 is a section on the line 1 1 of Fig. 6 showing a retaining device;

Fig. 8 is a section on the line 8 8 of Fig. 6 through one of the surface contact adjusting mechanisms;

Fig. 9 is a section on the line 9 9 of Fig. 6 giving an end view of one of the surface contact adjusting mechanisms;

Fig. 10 is a section of one of the surface contact adjusting mechanisms taken on the line N lll of Fig 6;

Fig. 11 is a section through one of the abrasive head rollers taken on the line l I I I of Figs. 1 and 2;

Fig. 12 is a vertical section on the line lil-l2 of Figs, l and 3 showing the height adjusting mechanism;

Fig. 13 is a detail showing of the height adjusting mechanism being a section on the line I3 I3 of Fig. 12;

Fig. 14 is a view of the gear reduction drive for the mechanism;

Fig. 15 is a view of the buiiing belt; and,

Fig. 15 is a sectional View thereof taken on the line |6 l6 of Fig. 15.

The machine includes an elongated bed or base 2E! adapted to rest on a suitable foundation, such as the floor. This bed has upstanding end portions connected by suitable front and rear braces, the end portions being .provided with journal track 30 thereon, the track being dovetailed onV one edge, as shown in Fig. 5. This track receives a supporting runner 3l of the abrading head, which runner is dovetailed to correspond with the front edge of the track 38, and is secured at the back edge of the track by a plate 32 bolted thereto as shown in Fig. 5.

bed of the machine beyond the limits of the plate 55. The plate is divided by a vertical supporting wall 64.

The belt supporting mechanism includes a frame formed primarily of two pieces 65 and 88 bolted together. 'Ihe member 55 is essentially a side wall to this frame, whereas the member 65 includes, not only the complementary side wall for the other side thereof, but also a connecting web 51 having spaces 63 therein to reduce the quantity of metal. Bolts 69 extend through the Y member 615 and into flanges 18 (dotted lines Fig.

The track 3i) is provided with an elongated opening 33 terminating short of the ends thereof. Each of the opposite ends of the track has a bearing 34 thereon medially located beneath the opening 33. A lathe screw 35 is journaled within the bearings 34 and extends completely through one of them,- as shown in Fig. 1.

The cylinder axis 25 extends beyond one o-f the journals 24 and has removably keyed thereto a gear 38. Beneath this gear 38 there is journaled a gear 39 (Fig. 14) meshing therewith, that in turn meshes with the drive gear 48 secured to a suitable power source. The power source thus drives the cylinder gear 38 through the intermediate idler 59. A second idler 4| meshes with the idler 39 and is journaled to the bed 28. The idler 4| in turn meshes with the third idler 42 mounted upon the base 28, which idler has rotating therewith a worm 43. The worm 43 meshes with a worm gear 44 mounted on a bearing 45 on the bed. In the particular arrangement here shown, the bearing 45 is a vertical journal and supports a countershaft 48 to which the worm gear 44 is secured. At the top of the shaft a bevel gear 41 is mounted, this gear,

therefore, receiving through the gear train power from the motor driven gear 49.

A pair of reversing bevel gears 48 and 4S (Figs. 14 and l) are both secured to the lead screw 35. In the manner usual to the art, the two gears 48 and 49 are parts of a reversing clutch operated in the usual manner in lathes to reverse the direction of rotation of the head screw as the carriage is brought to each end of its travel. Details of this reversing mechanism are not shown.

The carriage runner 3| has a depending internally threaded boss 55 thereon extending into the opening 33 of the track member 38.. The boss 50 receives the head screw 35 whereupon the runner 3| is caused by the screw to reciprocate back and forth across the bed.

A more or less U-shaped flanged plate 55 is bolted as at 58 to the runner 3|. The upper surface of the plate 55 has a circular opening 51 therein (Figs. 5 and 1l) that receives a corresponding circular boss 58 on a head support 59. A clamp element 55 extends in from the bottom of the hole 51 and is bolted into the circular boss 58 by screws 9|. As is shown in Fig. 11, a small space exists between the clamping element 68 and the boss 58 so that the binding effect in this connection may be adjusted. The connection permits rotary adjustment of the support 59 and normally is suciently tight to hold the support 59 to the head elements thereon in adjusted position while permitting them to be moved manually.

The plate 59 -extends lateral-1y to overhang the 3) depending from the connecting web 81 of the member 66 whereby to secure the two together as an integral unit.

The member at its inner end extends over the support 59 adjacent the wall 54. The wall is provided with a central opening 1 I around which on one side is a circular bearing surface 12, and spaced therefrom an additional arcuate bearing surface 13 extending approximately threequarters of the way around the opening as shown in Fig. 3. The wall 84 has spokes projecting between the surfaces 12 and 13, these spokes being integral with the Wall, as are shown in Fig. 3. On the face of. the wall 64 opposite the aforementioned surfaces, there is a short arcuate shelf 14, terminating at one end in a stop-shelf 15 for a purpose to be described.

The end of the member 85 is flanged, as shown at 16 and 11, the latter having an arcuate extension (Fig. 3). The flange 11 extends slightly over the opening 1| and has a lateral wall flush with the bearing surface 13. Therebeyond, the member B5 extends inwardly along an edge 18 to an arcuate portion 19 that rests within the arcuate shelf 14. The member 65 also has a circular boss 88 that ts in bearing relation within the opening 1| of the wall 64.

A substantially arcuate dished clamping plate 8| fits over the wall 84 opposite the member 65. This plate 8| has an arcuate portion 82 screwed to the arcuate portion of the flange 11 by screws 83. The plate 8| has a circular boss 84 tting within the opening 1| opposite the boss 80 on the frame member 85. Around this boss it is provided with a circular bearing surface to cooperate with the surface 12 on the wall 64, and an arcuate bearing surface to cooperate with the bearing surface 13. It will be observed that the arcuate extent of the surface 13 is somewhat greater than the plate 8|.

Screws 85 extend through the plate 8|, its boss 84, and into the boss 88 of the frame member 65. A space between the two bosses permits the bolts to be tightened as necessary to hold the parts together, but with enough freedom to allow the frame 65 to be swung upwardly about the wall until the edge 18 strikes the ledge 15. Preferably this movement is somewhat over so that the frame will rest in its lifted position. In this movement the plate turns on the surfaces 12 and 13, and the member 65 turns about the opposite face of the wall 84, with the arcuate portion 19 of the frame riding on the arcuate ledge 14.

A motor 85 is mounted on the support 59 outside of the wall 94. This motor has a shaft 81 extending through central bores in the plate 8|, and the frame member 65, and through the opening 1|. A frictionless bearing 88 in the boss 84 supports the shaft. An additional bearing 89 in the frame member 66 supports the other end of the shaft. Between the frame members a roller 90 is keyed to the shaft 88. A resilient outer cover 9| surrounds the roller.

The member 59 is provided with a pair of ears 92 extending from one edge thereof. A threaded sleeve 93 is pivoted at 94 between the two ears. A threaded rod 95 is received into the sleeve 93. This rod extends through the member 65 to the top thereof above the flange 16, and has turning handles 95 secured to its upper end. The flange 15 of the member 55 has an internally threaded boss 91 at the place where the rod 95 extends therethrough. The rod 95 has on it a ball section 98 located within the threaded boss. Complementary caps 99 and |90 are 4extended into the threaded boss against the ball section 93 and are secured therein by set screws as shown. Kerfs are provided in the bearing cap elements for their manipulation. The two bearing caps engage the ball section to provide a supporting means to maintain the position of the frame as it is pivoted about the wall 96.. As is evident, rotation of the handles 96 by the threaded engagement between the rod 95 and the sleeve 93 raises or lowers the frame about the wall 64.

At the outer end of the frame, there is provided a shaft |93, which shaft is mounted in blockshaped bearing boxes` |04, there being one such box for each side of the frame. The bearing boxes |94 are supported on slides in openings |65 in the sides of the frame wherein they may move axially of the frame. Each bearing box has a threaded extension |56 passing through a flange |91 of each of the sides of the frame. A pair of nuts |93 are mounted on the extensions |35 whereby to limit the inward movement of the axle |53 and to lock the adjustment. Thus, each end of the axle may be adjusted separately within the limits of the lost motion of the mountings.

A tension adjusting means is provided in the form of three rollers conveniently located adjacent the outer roller |52. This means includes opposite brackets HD mounted on the frame members 65 and 65 and supporting between them an idler roller Similar brackets ||2 support an idler roller H3 spaced a short distance from the roller 'Between these two rollers, there are provided spaced brackets ||4 having dovetailed vertical slots in them as shown. Supporting members ||5 are held to slide vertically within the slots. A tension roller I6 is mounted between the members I5. Adjacent the bottoms of the slots of the brackets ||4 are horizontal ledges ||1 through which are threaded screws ||8 that abut corresponding ledges ||9 on the elements H5. Thus, adjustment of the screws ||8 elevates or lowers the roller H6. Lock nuts are provided on the screws to held them in adjusted positions.

Mechanisms consisting of a pair of horizontally and vertically adjustable rollers are also provided for adjusting the area of contact between the belt and the cylinder. On each of the side members 35 and 35 there is secured a track member |22. Each track member is dovetailed, as shown in Fig. 10, to provide horizontal runners.

A pair of rollers |23 and |24 are mounted on the slides |22. The rollers are supported in mechanisms providing for vertical and horizontal adjustments, and these mechanisms are all similar save that the two on each side are opposite to each other. Consequently, a description of one mounting will suiiice for all.

The roller |23 has a resilient outer covering |25. It is supported upon an axis '|26 that in turn is received in opposite bearing blocks |21 joined by a connecting bar |28. Each bearing block has a threaded rod |29 extending upwardly from it, the rods being surrounded by coil springs |39. The rods |29 extend through ledges |3| on vertically adjustable slides |32 and nuts |33 are located above the ledges to secure the rods. The bearing blocks are guided toward the bottom by walls |34 also on the vertical slides |32. Thus, Vthe bearing blocks may be individually drawn up or let down by adjustment of the nuts |33 which changes the tension of the springs |39.

The slides |32 are dovetailed to engage in corresponding tracks |35 in horizontally adjustable slides |35. The vertical slides likewise have openings |31 in them, one edge |39 of which is formed as a rack. A shaft |39 is journaled in the opposite horizontal slides |35` and extends completely across and outside both sides of the frame. This shaft |39 extends through both openings |31 and within them has gears |40 secured to it. These gears mesh with the racks |38. Handles |4| are secured to the opposite projecting ends of the shaft |39 for the purpose of turning the shaft. From the foregoing it will be seen that turning either handle |4| rotates the shaft |39, turning both gears |49 and simultaneously adjusting both of the vertical slides |32 to which is secured the roller |23.

The horizontal slides |35 are dovetailed to ride upon corresponding dovetails of the main tracks |22. The upper edges of the horizontal slides |36 are formed into racks |22. A shaft |23 is journaled in the members 65 and 55 of the frame and extends completely across and through these sides. Outside of the two side members gears M4 are secured to mesh with the racks H22 on the horizontal slides. Handles |45 are secured to opposite ends of the shaft |43. Thus, rotation of either handle |45 rotates the shaft |43 and both gears |44 to shift both horizontal slides |35. Necessarily the vertical slides are carried with the horizontal slides, being mounted on them. In order to accommodate for the horizontal displacement of the shafts |39 upon movement of the horizontal slides, slots |46 are provided in the side members 65 and 6B of the frame.

The adjusting mechanism for the roller |24 is identical with lthat for the roller |23, but is arranged oppositely thereto. In connection with the roller 24, in Eig. 6, are shown lock means for the several adjustments. The vertical slide |32 Iat one edge is provided with a series of openings |51. A plate |58 is secured to the horizontal slide (Fig. 8) and overlies the edge of the vertical slide containing the holes |111. To the plate |48 are secured opposed ears |49 between which is pivoted a lever |59. This lever has pivoted to one of its ends -a pin |5| that passes through a hole in the plate U23 and may selectively be engaged in any of the holes |51. A spring |52 located between 'the plate |48 and the other handle end |53 of the lever |59 maintains the pin 5| inwardly into engagement with one of the holes |131. The ypin may be freed by depressing the handle end |53 of the lever. It will be seen that .adjustment by rotation of the handles |4| may be had only after the pins |55 are freed. Of course, it is necessary .to have this lock on only one side in view of the rigid connection eifected by the shafts |39 and their several gears.

For locking the horizontal slides there are mounted on Athe member 35 a pair of spring blades |55. Each blade |55 has a pin |59 extending through the ange on the member 63 .and engageable between teeth on the gears |44. The spring blades |55 normally urge the pins |56 out of engagement with the gear-s |44. However, rthe free ends of the spring blades are forked as at |51 and surround screws |58. Nuts |59 are engaged over the screws |53 and may be threaded 4down vto force the spring-blades correspondingly down .to put the pins i56 against the gears |44.

The belt |65 is shown in Fig. 1 to have an -irregular edge. This edge i-s more or less lscalloped to avoid the scarring action of a straight edged belt. A buffing belt, such as in Figs. and 16, may be used. It preferably is of a leather base part |51 to which are secured .a series of spaced pads |68 of felt or like material. The pads are so arra-nged as to be out .of Contact with each other, but to overlap.

The operation of the mechanism is a-s follows:

The frame is turned up about its pivot including the boss 80 engaging in the `opening 1| in the wall 84 until stopped by engagement of the edge 18 with the ledge 15. The bearing brackets 23 are opened and the cylinder 26, duly coated with copper but unpolished, is shifted into position within the bearing blocks 2|. The arms 23 vare then clos-ed down and secured into position by the screws 21.

The frame then is turned down over the cylinder and the `rod 95 engaged into the sleeve 93 controlling the limit of the downward movement of the frame and providing `for a iine adjustment thereof. The entire frame is then adjusted manually about its pivot at 58 to a proper angular position relative to the axis of the cylinder, which may be perpendicular thereto, as shown in full lines cf Fgi. 1, or may be .at som-e angle thereto, as shown in dotted lines in that figure. The angular position reduc-es whip in the belt and increases the area of contact.

In order to compensate for any inequalities in .the length of the -belt between its two sides, the nuts |08 are adjusted individually to draw the -bearing blocks |04 out until the tension is the same across the belt. The tension of the belt also may-be controlled by adjusting the screws H8 to lift the roller ||5 of the belt tensioning mechanism.

The :area of contact of the Ibelt with the cylinder i-s determined in part by the adjustment of the handles 96 that raise and lower the entire frame relative to .the cylinder. Following this adjustment, the lock pins fare rel-eased, and the handles |45 are turned, shifting the horizonltal slides inwardly or outwardly, as the case may be, which properly places the rollers |23 and |24 preferably equally spaced on opposite sides of the axis of the cylinder, and also places these slides in proper position for adjustment of the vertical slides by the handles |4|. |59 are turn-ed down to force :the pins |56 against the gears |44. The lock pins |5| are released by depression of the handles |53 and the handles |4| are turned to raise or lower the rollers. The lock pin-s |5| are then permitted to engage in the adjacent holes |41. As is perfectly evident, these two adjustments determine the area of contact between the belt and the cylinder.

The motor driving the power gear 40 is then started to cause the gear 38 to be rotated, driving the cylinder at a `proper speed and, at the same time, the gear 40 produces rotation of the screw 35 that, through engagement with the depending member 58 of the runner 3|, moves the entire head in one direction -or-the other axially of the After this, the nuts cylinder. It is, of course, understood that at the end of each reciprocation of the head to one end of the cylinder, the screw 35 is automatically reverse-d in Ithe manner well known in the art and suggested in Fig. 14, so that the head is then moved inl the other direction toward the other end of the cylinder.

The motor 86 is put in operati-on at this time and may lbe connected so as to -be energized simultaneously with the energization of the source of power driving the gear 40. The motor 86 causes rotation of the shaft 81, which shaft, being keyed thereto, drives the roller 90 about which the belt travels. The belt then travels -about the roller, through the tension mechanism, about the roller |02, beneath the rollers |23 and |24, and over the lcy-linder 26. Preferably the speed of operation of the motor 86 is relatively high, being in the neighborhood of 4000 R. P. M.

With the belt thus in motion, the abrasive action is manifestly unidirectional and substantially perpendicular to the generatrix of the cylinder 26. The rotation of the cylinder, of course, distributes the polishing action completely around the surface and .the reciprocal movement of the head by the screw 35 distributes this movement over the entire length of the cylinder.

As noted, the angular disposition of the head, shown in dotted lines in Fig. 1, reduces the whip of .the belt. The irregular edge of the belt eliminates any edge markings produced by a belt having a straight edge.

The practice of the method is as follows:

In the manufacture o-f th-ese photoengraving cylinders, the cylinders are duly coated with copper of the proper diameter and polished. The surface must be .thoroughly free of scratches. After the cylinders are finished, they are then processed to engrave the pictures, or the like, onto them by a chemical process kno-wn in the art. Necessarily, this engraving penetrates Iben-eath the outer surface of the cylinder in the parts that are to be inked. Ink is then distributed over `the cylinders and the excess is scraped off by the rotating cylinders against a knife blade that is contiguous to the normal diameter of the cylinder but, of cour-se, spaced outwardly from the portions that are engraved. This blade scrapes the ink away from the normal surface of `the cylinder and leaves the engraved portions filled with ink that will print.

If there be present on the cylinders any markings .or scratches, ink will be entrapped in them and will print out onto the paper. Where the polishing marks are not unidirectional and where they are at an acute angle relative to the knife blade, ink will be entrapped in them. Intersections are a particular problem, sin'ce, frequently, they are deeper even than single abrasive scratches and they also form pockets to trap Y the ink.

In the `present method, the polishing is done by applying an abrasive in a single direction around the cylinder. More particularly, the

l method includes automatically passing an abrahends abrading the surface without applying a direct pressure against the surface. The contact between the belt and the cylinders is between the two rollers |50. Between these rollers, the belt may yield away from the cylindrical surface in a degree determined by its tension. There is no positive head resting against the abrasive material to hold it on the cylinder. Thus, should a particle of abrasive or like material come between the belt and the cylinder, the inherent elasticity of the belt will cause the belt to yield and carry this particle of abrasive out without its digging into the surface of the cylinder.

In practicing the method, it is rst proposed to traverse the surface of the cylinder with a relatively coarse abrasive. Thereafter, a buffer belt, such as shown in Figs. and 16, may be employed to add the final ni'sh. The irregular surfaces provided by the pads on the buffer belt break up any streaking effects of abrasive dust, and prevent clotting of particular parts of the belt, with resultant scratching.

The bufng alction need not necessarily be used. Sometimes in place or using a second belt, turpentine or like material can be applied to the original belt after it has done its first polishing. This turpentine causes the belt to collect particles of copper upon further running, which copper collects on the belt between the interstices of the abrasive, to reduce the abrading eiect, and to produce a, burnishing one.

This process not only produces a far superior surface on the cylinder, but also does so in a very much shorter time than has formerly been required. With heretofore known means, it has required, for example, three hours for polishing a cylinder of a certain type. With the present process, a superior surface can be put on the cylinder in from twenty to thirty minutes.

From the foregoing, it may be seen that a new and greatly advantageous method has been .provided. It is known that more or less similar means have been used for polishing other surfaces, but never in connection with and following the steps of the present method. Furthermore, a machine has been provided disclosing one most advantageous way of producing the method.

What is claimed is:

1. In a polishing machine for photoengraving cylinders, a bed, means to hold the cylinder thereon, a head, an endless belt polishing medium on the head, means driving the `belt across the surface of the cylinder, and the belt having an irregular edge to avoid edge markings on the cylinder.

2. In a mechanism of the kind described, a bed, a head mounted for movement across the bed, a frame mounted on said head, said frame extending across the bed, rollers, one at e'ach end of the frame, an endless belt polishing medium mounted on said rollers, means supporting the frame at one end on .the head for pivoting movement about a horizontal axis, and screw means interengaging between the head an-d the frame for pivoting the frame.

3. In a mechanism of the kind described, a bed, a head mounted for movement across the bed, a frame mounted on said head, said frame extending a-cross the bed, rollers, one at eac-h end of the frame, an endless belt polishing medium mounted on said rollers, means supporting the frame at one end on the head for pivoting movement about a horizontal axis, and screw means interengaging between the head and the frame for pivoting the frame, said screw means including a screw, means supporting the screw on the frame against axial movement but for lateral movement to accommodate for displacement of the axis of the screw relative .to .the frame when the fra-me is pivoted on the head.

4. In a mechanism of the kind described, a bed for supporting an object to be polished, a hea'd on the bed extending across the object, an endless belt abrasive on the frame and movable across the object, means for directing the abrasive onto the object including two slides mounted on the head, one on each si'de thereof, said slides being mounted for displacement on the head, a contact means supported between the slides to act on the abrasive, and means acting on both slides at once to dispiace them together for adjusting said .contact means.

5. In a mechanism of the kind described, al

bed for supporting an object to be polished, a hea'd on the bed extending across the object, an endless belt abrasive on the frame and movable across the object, means for directing the abrasive onto the object including slides on opposite sides of the frame, contact means supported between the slides to act on the abrasive, means mounting the slides for movement in a first plane, means moving said slides together in said rst plane, means mounting .the slides for movement in a second plane, and means moving the slides together in said second plane.

6. In a polishing machine, a bed to hold 'a cylinder to be polished, a head, an endless belt polishing device on the head and adapted to be swung over .the cylinder so that the belt may traverse the surface thereof, means to limit the swinging of the head to determine the pressure of the belt on .the cylinder, and means to adjust the limiting means.

FRANK E. YETTER. 

